The present invention relates to novel compositions comprising particular polysiloxane-polyoxyalkylene polymers and to the use of such compositions in the manufacture of urethane cellular products, particularly flame-retarded flexible polyether polyol-based urethane foam.
Our aforementioned copending application Ser. No. 279,883, filed Aug. 11, 1972, now U.S. Pat. No. 3,846,462 provides a particular class of cyanoalkyl- and/or cyanoalkoxy-modified polysiloxane-polyoxyalkylene block polymers which are especially useful as foam stabilizers of polyether polyol-based urethane foam. As described in said application, such polymers have a highly desirable combination of properties. One such property is good surfactant potency from the standpoint of both (1) the measured original height to which the foam rises as it is being formed and (2) the ability to maintain the original height of the foam once it has formed.
Another highly desirable property of the aforesaid class of cyano-bearing polymers is their good processing latitude, that is, the ability to provide foams of satisfactory quality over a relatively wide range of operating variables, such as, for example, variation in polymer concentration and in the concentration of metal co-catalysts which are normally employed in the manufacture of flexible polyether-based foams. The more common co-catalysts are organic derivatives of tin and thus sensitivity to variation in co-catalyst concentration is more particularly referred to in the art as "tin operating latitude." Decreasing the concentration of such co-catalysts below normal levels is sometimes necessary to improve foam breathability but, if the effectiveness of the foam stabilizer is narrowly dependent on co-catalyst concentration (that is, its tin operating latitude is poor), the desired enhanced breathability will be offset by foam weakness due to split formation. It is evident, therefore, that the good tin operating latitude of our aforesaid class of cyano-bearing polymers is a significant property.
In addition to good potency and processing latitude, our aforesaid cyano-bearing polysiloxane-polyoxyalkylene polymers possess the further highly desirable property of allowing for the formation of flame-retarded, polyether urethane foam of relatively low burning extent and high porosity (as opposed to "tight" foam and as reflected by foam breathability).
Notwithstanding the aforementioned excellent combination of properties exhibited by the cyano-modified polysiloxane-polyoxyalkylene block copolymers of our aforementioned application, it has been found that, when employed as the foam stabilizing component of foam formulations having low density foam specifications, such polymers often provide foam having a density which is higher than the density specification with a corresponding production of less foam per unit volume. Although the foam product is acceptable and useful and, although the numerical value of the density may only be slightly higher than desired, the consequential production of less foam per unit volume is of significant concern to the large scale producer of urethane foam. It is desirable, therefore, and is a primary object of this invention to provide foam stabilizing compositions which allow for minimization of this particular problem without substantial sacrifice of the highly desirable combination of properties possessed by our aforementioned class of cyano-bearing polysiloxane-polyoxyalkylene polymers. Various other objects and advantages of this invention will become apparent to those of ordinary skill in the art from the accompanying description and disclosure.